Mar.4 (GMM) Bridgestone's tyres for the 2010 season will feature a bigger difference between the widths of the fronts and rears, a report in Germany's Auto Motor und Sport magazine claims.

Some teams at Jerez this week have been testing proposed changes to the Japanese supplier's products for next year.

It is said that, due to the reintroduction of slicks this year at the same time as radical changes to the aerodynamic regulations - as well as the introduction of KERS - the dimensions of the 2009-specification tyres are producing more than expected levels of rear wear.

F1's governing FIA has reportedly asked Bridgestone to change the ratio of tyre width for its 2010 tyres, either by widening the rears, or supplying a narrower front tyre.

"We have to admit that we made a mistake," FIA president Max Mosley is quoted as saying. "We should have anticipated that the rear tyres would be a weak point."

The result, in 2009, is that by producing a better car balance by moving the weight distribution overly forwards, the benefit of the KERS energy re-use systems is effectively negated.

Mosley confirmed: "We will ask Bridgestone to change the tyre dimensions for 2010."